U.S. patent application number 12/033851 was filed with the patent office on 2008-10-02 for manufacturing method for micro-sd flash memory card.
This patent application is currently assigned to Super Talent Electronics, Inc.. Invention is credited to Siew S. Hiew, Paul Hsueh, Charles C. Lee, Abraham C. Ma, Ming-Shiang Shen.
Application Number | 20080235939 12/033851 |
Document ID | / |
Family ID | 43981443 |
Filed Date | 2008-10-02 |
United States Patent
Application |
20080235939 |
Kind Code |
A1 |
Hiew; Siew S. ; et
al. |
October 2, 2008 |
Manufacturing Method For Micro-SD Flash Memory Card
Abstract
A method for fabricating MicroSD devices includes forming a PCB
panel having multiple PCB regions arranged in parallel rows.
Passive components are attached by conventional surface mount
technology (SMT) techniques. IC chips, including a MicroSD
controller chip and a flash memory chip, are attached to the PCB by
wire bonding or other chip-on-board (COB) technique. A molded layer
is then formed over the IC chips and passive components using a
mold that prevents formation of plastic on the upper surface of
each PCB. The panel is then singulated using one of a laser cutting
method, an abrasive water jet cutting method, and a mechanical
grinding method such that the resulting PCB substrate and plastic
housing have the width, height and length specified by MicroSD
specifications. A front edge chamfer process is then performed.
Inventors: |
Hiew; Siew S.; (San Jose,
CA) ; Lee; Charles C.; (Cupertino, CA) ;
Hsueh; Paul; (Concord, CA) ; Ma; Abraham C.;
(Fremont, CA) ; Shen; Ming-Shiang; (Taipei Hsien,
TW) |
Correspondence
Address: |
BEVER HOFFMAN & HARMS, LLP;2099 Gateway Place
Suite 320
San Jose
CA
95110
US
|
Assignee: |
Super Talent Electronics,
Inc.
San Jose
CA
|
Family ID: |
43981443 |
Appl. No.: |
12/033851 |
Filed: |
February 19, 2008 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10888282 |
Jul 8, 2004 |
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12033851 |
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11773830 |
Jul 5, 2007 |
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10888282 |
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11309594 |
Aug 28, 2006 |
7383362 |
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11773830 |
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10707277 |
Dec 2, 2003 |
7103684 |
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11309594 |
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10913868 |
Aug 6, 2004 |
7264992 |
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10707277 |
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11624667 |
Jan 18, 2007 |
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10913868 |
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09478720 |
Jan 6, 2000 |
7257714 |
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11624667 |
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09366976 |
Aug 4, 1999 |
6547130 |
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09478720 |
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12025706 |
Feb 4, 2008 |
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09366976 |
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Current U.S.
Class: |
29/831 ; 29/841;
365/185.33 |
Current CPC
Class: |
H01L 24/97 20130101;
H05K 2203/0228 20130101; H01L 2224/48227 20130101; Y10T 29/49126
20150115; H01L 2924/1815 20130101; H05K 2203/0746 20130101; H05K
1/117 20130101; Y10T 29/49147 20150115; Y10T 29/49171 20150115;
H01L 21/561 20130101; H05K 3/0052 20130101; H01L 2924/14 20130101;
H05K 2201/09154 20130101; H05K 3/0032 20130101; H01L 2224/97
20130101; Y10T 29/49146 20150115; H01L 2924/01029 20130101; H01L
2224/97 20130101; Y10T 29/49128 20150115; H05K 3/284 20130101; H01L
2224/85 20130101; Y10T 29/49789 20150115; H05K 2201/10159 20130101;
Y10T 29/49798 20150115; H01L 2924/14 20130101; H01L 2924/00
20130101; H05K 2203/1316 20130101 |
Class at
Publication: |
29/831 ;
365/185.33; 29/841 |
International
Class: |
H05K 3/20 20060101
H05K003/20; G11C 11/34 20060101 G11C011/34 |
Claims
1. A method for producing a plurality of memory card devices,
having predefined width and height specifications, the method
comprising: producing a printed circuit board (PCB) panel including
a plurality of PCB regions; attaching at least one passive
component and at least one integrated circuit to each said PCB
region; forming a single-piece molded layer on the second surface
of the PCB panel such that said at least one passive component and
said at least one IC die of each PCB region are covered by thermal
set plastic, wherein a combined thickness of said PCB panel and
said single-piece molded layer is equal to said height
specification; and singulating said PCB panel and molded layer by
cutting said PCB panel and said molded layer such that the PCB
panel is separated into said plurality of memory card devices,
wherein each memory card device includes a printed circuit board
having a width that is equal to said predefined width
specification.
2. The method according to claim 1, wherein producing said PCB
panel comprises forming each said PCB region to include opposing
first and second surfaces, a plurality of metal contacts disposed
on the first surface, a plurality of first contact pads disposed on
the second surface, a plurality of second contact pads disposed on
the second surface, and a plurality of conductive traces formed on
the PCB region such that each conductive trace is electrically
connected to at least one of an associated metal contact, a first
contact pad and a second contact pad; and wherein attaching said at
least one passive component and said at least one integrated
circuit to each said PCB comprises: attaching said at least one
passive component to the first contact pads using a surface mount
technique, and attaching said at least one unpackaged integrated
circuit (IC) die to the second contact pads using a chip-on-board
technique.
3. The method of claim 2, wherein attaching said at least one
passive component comprises: printing a solder paste on said first
contact pads; mounting said at least one component on said first
contact pads; and reflowing the solder paste such that said at
least one component is fixedly soldered to said first contact
pads.
4. The method of claim 2, further comprising grinding a wafer
including said at least one IC die such that a thickness of said
wafer is reduced during said grinding, and then dicing said wafer
to provide said at least one IC die.
5. The method of claim 4, wherein attaching at least one IC die
comprises bonding a first IC die to the second surface of the PCB
and wire bonding the first IC die to said second contact pad.
6. The method of claim 5, wherein attaching at least one IC die
further comprises bonding a second IC die to the first IC die, and
wire bonding wire bonding the second IC die to a third contact
pad.
7. The method according to claim 1, wherein forming said
single-piece molded layer comprises disposing said PCB panel into a
first molding die, said first molding die comprises a plurality of
alignment poles, and wherein disposing said PCB panel comprises
operably engaging said alignment poles into corresponding alignment
holes defined in said PCB panel.
8. The method according to claim 1, wherein singulating said PCB
panel after forming said single-piece molded layer comprises
cutting said PCB panel and said molded layer using one of a laser
cutter, a water jet cutter, and a saw, whereby a PCB substrate is
separated from said PCB panel, and a molded is separated from said
molded layer.
9. The method according to claim 7, further comprising mechanically
grinding a peripheral edge of each of said plurality of memory card
devices.
10. The method according to claim 1, wherein said memory card
devices comprise MicroSD devices, and wherein singulating
comprising forming a peripheral edge of said PC substrate and
peripheral walls of said molded housing such that both said
peripheral edge and said peripheral walls define a width of 11 mm,
and a combined thickness of said substrate and said molded housing
is in the range of 0.7 mm to 1.0 mm.
11. A MicroSD device comprising: a printed circuit board assembly
(PCBA) including: a printed circuit board (PCB) having opposing
first and second surfaces, and a peripheral edge extending between
the first and second surfaces, a plurality of metal contacts
disposed on the first surface of the PCB, at least one passive
component mounted on the second surface of the PCB, at least one
unpackaged integrated circuit (IC) die mounted on the second
surface of the PCB, and a plurality of conductive traces formed on
the PCB such that each conductive trace is electrically connected
to at least one of an associated metal contact, said at least one
IC die and said at least one passive component; and a single-piece
molded housing formed on the second surface of the PCBA such that
said at least one passive component and said at least one IC die
are covered by said molded housing, and such that substantially all
of the peripheral edge of the PCB is exposed, wherein said
peripheral edge of said PCB and peripheral walls of said molded
housing are formed such that both said peripheral edge and said
peripheral walls define a nominal width of approximately 11 mm, and
a combined thickness of said PCB and said molded housing is in the
range of 0.7 to 1.0 mm.
Description
RELATED APPLICATIONS
[0001] This application is a continuation-in-part (CIP) of U.S.
Patent application for "Manufacturing Method For Memory Card", U.S.
application Ser. No. 10/888,282, filed Jul. 8, 2004.
[0002] This application is a also a CIP of U.S. Patent application
for "MOLDING METHODS TO MANUFACTURE SINGLE-CHIP CHIP-ON-BOARD USB
DEVICE", U.S. application Ser. No. 11/773,830, filed Jul. 5, 2007,
which is a CIP of "Single-Chip Multi-Media Card/Secure Digital
(MMC/SD) Controller Reading Power-On Boot Code from Integrated
Flash Memory for User Storage", U.S. application Ser. No.
11/309,594, filed Aug. 28, 2006, which is a CIP of "Single-Chip USB
Controller Reading Power-On Boot Code from Integrated Flash Memory
for User Storage", U.S. application Ser. No. 10/707,277, filed Dec.
2, 2003, now U.S. Pat. No. 7,103,684.
[0003] This application is also a CIP of U.S. Patent application
for "Removable Flash Integrated Memory Module Card and Method of
Manufacture" U.S. application Ser. No. 10/913,868, filed Aug. 6,
2004.
[0004] This application is also a CIP of U.S. Patent application
for "Electronic Data Storage Medium with Fingerprint Verification
Capability", U.S. application Ser. No. 11/624,667, filed Jan. 18,
2007, which is a divisional of U.S. Patent application for
"Electronic Data Storage Medium with Fingerprint Verification
Capability", U.S. application Ser. No. 09/478,720 filed Jan. 6,
2000, now U.S. Pat. No. 7,257,714, which has been petitioned
claiming benefit of Continuation-In-Process status of one of
inventor's earlier U.S. Patent application for "INTEGRATED CIRCUIT
CARD WITH FINGERPRINT VERIFICATION CAPABILITY", U.S. application
Ser. No. 09/366,976, filed Aug. 4, 1999, now issued as U.S. Pat.
No. 6,547,130.
[0005] This application is also a CIP of U.S. Patent application
for "Methods and systems of managing memory addresses in a large
capacity multi-level cell (MLC) based flash memory device", U.S.
application Ser. No. 12/025,706, filed Feb. 4, 2008.
FIELD OF THE INVENTION
[0006] This invention relates to portable electronic devices, and
more particularly to portable memory card devices such as those
that utilize the Secure-Digital (SD) and Micro Secure-Digital
(MicroSD) specifications.
BACKGROUND OF THE INVENTION
[0007] A card-type electronic apparatus containing a memory device
(e.g., an electrically erasable programmable read-only memory
(EEPROM) or "flash" memory chip) and other semiconductor components
is referred to as a memory card. Typical memory cards include a
printed circuit board assembly (PCBA) mounted or molded inside a
protective housing or casing. The PCBA typically includes a printed
circuit substrate (referred to herein simply as a "substrate")
formed using known printed circuit board fabrication techniques,
with the memory device and additional components (e.g., control
circuitry, resistors, capacitors, inductors, etc.) formed on an
upper surface of the substrate (i.e., inside the casing), and one
or more rows of contact pads exposed on a lower surface of the
substrate. The contact pads are typically aligned in a width
direction of the casing, and serve to electrically connect and
transmit electrical signals between the memory chip/control
circuitry and a card-hosting device (e.g., a computer circuit board
or a digital camera). Examples of such portable memory cards
include multi media cards (MMC cards), personal computer memory
card international association (PCMCIA) cards. An exemplary MMC
card form factor is 24 mm wide, 32 mm long, and 1.4 mm or 1.5 mm
thick, and is substantially rectangular except for a chamfer formed
in one corner, which defines the front end of the card that is
inserted into a card-hosting device. The card's contact pads are
exposed on its lower surface of each card near the front end. These
and other similar card-like structures are collectively referred to
herein as "memory module cards" or simply as "memory cards".
[0008] An important aspect of most memory card structures is that
they meet size specifications for a given memory card type. In
particular, the size of the casing or housing, and more
particularly the width and thickness (height) of the
casing/housing, must be precisely formed so that the memory card
can be received within a corresponding slot (or other docking
structure) formed on an associated card-hosting device. For
example, using the MMC card specifications mentioned above, each
MMC card must meet the specified 24 mm width and 1.4/1.5 mm
thickness specifications in order to be usable in devices that
support this MMC card type. That is, if the width/thickness
specifications of a memory card are too small or too large, then
the card can either fail to make the necessary contact
pad-to-card-hosting device connections, or fail to fit within the
corresponding slot of the associated card-hosting device.
[0009] MicroSD is a format for removable flash memory cards that is
used mainly in mobile telephones, handheld GPS devices, portable
audio players, video game consoles and expandable USB flash memory
drives. It is currently (2007) the smallest memory card available
commercially, and is about a quarter the size of an SD card, and is
currently available with memory capacities ranging from 64 MB to 6
GB (with 8 GB devices announced). Present MicroSD manufacturing
methods chip-on-board (COB) processes on a solid printed circuit
board (PCB) panel on which a 5.times.3 array of MicroSD PCBs are
printed. Conventional MicroSD production methods are similar to MMC
production methods.
[0010] FIGS. 29(A) and 29(B) depict a conventional method for
manufacturing a conventional micro-SD memory card 50 that meets
required size specifications in which a pre-molded cover or housing
54 is adhesively attached to PCBA substrate 52 over the
semiconductor components (which are disposed on the lower side of
substrate 52, and hence not shown in FIG. 29(A). FIGS. 30(A) and
30(B) show an alternative conventional microSD device 60 in which a
PCBA substrate 62 is mounted inside a pre-molded two sided package
including a base 64 defining a large enough cavity to hold the
rectangular PCBA substrate 62, and a cover 66 that is attached by
gluing or other means over PCBA substrate 62. The outlines of the
micro-SD housings 54 and 64 are pre-molded to meet the size and
shape specifications.
[0011] One shortcoming of the conventional manufacturing methods
include that the housings/covers is necessarily relatively thick,
and therefore takes up a significant amount of the specified memory
card thickness. As a result, the choice of memory device and other
components mounted used in these memory cards is limited to devices
that are relatively thin. In addition, because the PCBA substrates
must be sized to fit within the housings, whose external dimensions
are fixed by specification, the size of the PCBA substrates is
necessarily smaller than the total device area, which limits the
chip "real estate" area that can be otherwise used to hold
electronic components (e.g., a larger, and hence less expensive,
memory chip). Further, because the conventional covers (e.g., cover
66, FIG. 30(A)) are fabricated separately and then attached to the
substrate using an adhesive, the use of such separate covers
increases production and assembly costs, and the covers can become
detached from the substrate. Moreover, the conventional housings
typically have an undesirable seam around their edges, and the
surface on the package side is not smooth due to the thin wall and
the glue impression that is created from the cavity and the
micro-SD flash memory block.
[0012] What is needed is a method for producing memory cards that
maximizes the usable PCB substrate area and avoids the problems
mentioned above that are associated with conventional pre-molded
housing techniques.
SUMMARY OF THE INVENTION
[0013] The present invention is directed to a method for producing
memory card (e.g., SD or MicroSD) devices in which a thermal
plastic material is used to form a continuous molded layer on a
surface of a PCB panel (substrate), and then the PCB panel material
and molded thermal plastic material are singulated (i.e., cut
and/or ground) along a peripheral edge such that peripheral edges
of both the remaining PCB material and the remaining molded
material have the same dimensions as that set forth by the target
memory card specifications. For example, when the method is used to
produce MicroSD cards, both the remaining PCB material and the
remaining molded casing have a width of 11 mm, a length of 15 mm,
and PCB material and molded material have a combined height of 0.7
mm. By producing memory card devices in this manner, the PCB
surface area is significantly increased over conventional methods,
where the PCB must be narrower than the memory card specification
in order to fit inside a pre-molded housing. Memory cards produced
by this method thus exhibit increased card capacity and
functionality due to the increased available PCB surface area for
mounting integrated circuits and other components. In addition, the
molded casing provides a physically rigid memory card by filling
gaps and spaces that are otherwise not filled when separate covers
are used. In addition, the molded casing enables the use of a wide
range of memory devices by allowing the casing material formed over
the memory device to be made extremely thin, or omitted
entirely.
[0014] In accordance with an embodiment of the present invention, a
method for producing Micro-SD devices includes forming a PCB panel
including multiple PCB regions arranged in rows and columns,
attaching at least one passive component and at least one
integrated circuit to each said PCB regions, molding a thermal
plastic material in a single, continuous layer over the passive
component and integrated circuit, and then singulating the PCB
panel and molded material using one of a laser cutter, a water jet
knife or mechanical grinding method to form the individual MicroSD
devices. Note that both the molded material and the PCB material
are cut during the same cutting process, whereby the remaining PCB
substrate has the same width and length as the overmolded plastic
housing, and the entire peripheral edge of the PCB substrate is
exposed. Each micro-SD PCB substrate includes standard (plug) metal
contacts that are formed on a first (e.g., upper) surface thereof,
and all IC components (e.g., MicroSD controller chip, flash memory
chip, etc.) are mounted on the opposite (e.g., lower) surface of
the PCB substrate that is covered with the molded housing. The
molding process is performed by placing the PCB panel into a
special plastic molding die such that the upper surface is pressed
against a flat bottom surface of the die to prevent plastic
formation on the standard metal contacts, and the plastic layer is
then molded over the IC components (i.e., over the lower surface of
the PCB). After the molding process and singulation processes, an
optional grinding step is used to generate a chamfer at the front
edge of each molded MicroSD device.
[0015] According to an aspect of the invention, passive components
are mounted onto the PCB panel using one or more standard surface
mount technology (SMT) techniques, and one or more integrated
circuit (IC) die (e.g., a MicroSD controller IC die and a flash
memory die) are mounted using chip-on-board (COB) techniques.
During the SMT process, the SMT-packaged passive components (e.g.,
capacitors and oscillators) are mounted onto contact pads disposed
on the PCB panel, and then known solder reflow techniques are
utilized to connect leads of the passive components to the contact
pads. During the subsequent COB process, the IC dies are secured
onto the PCB using know die-bonding techniques, and then
electrically connected to corresponding contact pads using, e.g.,
known wire bonding techniques. After the COB process is completed,
the housing is formed over the passive components and IC dies using
plastic molding techniques. By combining SMT and COB manufacturing
techniques to produce MicroSD devices, the present invention
provides an advantage over conventional manufacturing methods that
utilize SMT techniques only in that overall manufacturing costs are
reduced by utilizing unpackaged controllers and flash devices
(i.e., by eliminating the cost associated with SMT-package normally
provided on the controllers and flash devices). Moreover, the
molded housing provides greater moisture and water resistance and
higher impact force resistance than that achieved using
conventional manufacturing methods. Therefore, the combined COB and
SMT method according to the present invention provides a less
expensive and higher quality (i.e., more reliable) memory product
than that possible using conventional SMT-only manufacturing
methods.
[0016] The present invention is also directed to a MicroSD device
generated in accordance with the novel method that includes a PCB
having components mounted thereon using the combined COB and SMT
method, and a molded plastic case that covers only the upper
surface of the PCBA, such that the side edges and the bottom
surface of the PCB substrate are exposed, with one edge having a
chamfered surface.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] These and other features, aspects and advantages of the
present invention will become better understood with regard to the
following description, appended claims, and accompanying drawings,
where:
[0018] FIG. 1 is a perspective top view showing an exemplary
MicroSD device according to an embodiment of the present
invention;
[0019] FIG. 2 is a cross sectional side view showing the exemplary
MicroSD of FIG. 1;
[0020] FIG. 3 is a flow diagram showing a method for producing the
MicroSD device of FIG. 1 according to another embodiment of the
present invention;
[0021] FIGS. 4(A) and 4(B) are bottom and top views showing a PCB
panel utilized in the method of FIG. 3;
[0022] FIG. 5 is a perspective view depicting a surface mount
technology (SMT) process for mounting passive components on a PCB
according to the method of FIG. 3;
[0023] FIG. 6 is a top view showing the PCB panel of FIG. 4(B)
after the SMT process is completed;
[0024] FIG. 7 is a simplified perspective view showing a
semiconductor wafer including integrated circuits (ICs) utilized in
the method of FIG. 3;
[0025] FIGS. 8(A), 8(B) and 8(C) are simplified cross-sectional
side views depicting a process of grinding and dicing the wafer of
FIG. 7 to produce IC dies;
[0026] FIG. 9 is a perspective view depicting a die bonding process
utilized to mount the IC dies of FIG. 8(C) on a PCB according to
the method of FIG. 3;
[0027] FIG. 10 is a top view showing the PCB panel of FIG. 6 after
the die bonding process is completed;
[0028] FIG. 11 is a perspective view depicting a PCB of the PCB
panel of FIG. 10 after a wire bonding process is performed to
connect the IC dies of FIG. 8(C) to corresponding contact pads
disposed on a PCB according to the method of FIG. 3;
[0029] FIG. 12 is a top view showing the PCB panel of FIG. 10 after
the wire bonding process is completed;
[0030] FIG. 13 is a perspective view showing a lower molding die
utilized in a molding process for forming a molded housing over the
PCB panel of FIG. 4(B) according to the method of FIG. 3;
[0031] FIG. 14 is a top plan view showing an upper molding die that
is used in conjunction with the lower molding die of FIG. 13 in the
molding process according to the method of FIG. 3;
[0032] FIGS. 15 is a top plan depicting a first step of mounting
the PCB panel of FIG. 12 into the lower molding die of FIG. 13
according to the method of FIG. 3;
[0033] FIGS. 16(A), 16(B) and 16(C) are simplified cross-sectional
side views depicting subsequent steps of assembling the molding die
and injecting molten plastic according to the method of FIG. 3;
[0034] FIG. 17 is a perspective bottom view showing the PCB panel
of FIG. 12 after the plastic molding process of FIGS. 16(A) to
16(C) is completed;
[0035] FIG. 18 is a top plan view showing the panel of FIG. 17
during a direct singulation process according to an embodiment of
the present invention; removed using one of the laser cutter of
FIG. 19 or the water jet knife of FIG. 20;
[0036] FIG. 19 is a simplified side view depicting the direct
singulation process of FIG. 18 using a laser cutter according to a
specific embodiment of the present invention;
[0037] FIG. 20 is a simplified side view depicting the direct
singulation process of FIG. 18 using a water jet knife according to
a specific embodiment of the present invention;
[0038] FIG. 21 is a simplified side view depicting the PCB panel of
FIG. 17 during an indirect singulation process in which the panel
is separated into individual blocks, each block including one
MicroSD device, according to another embodiment of the present
invention;
[0039] FIG. 22 is simplified top view depicting the individual
blocks after completion of the separation process of FIG. 21;
[0040] FIG. 23 is a simplified side view depicting a grinding
process during which the side edges of each block of FIG. 22 is
trimmed according to another embodiment of the present
invention;
[0041] FIG. 24 is simplified top view depicting the individual
MicroSD devices after completion of the grinding process of FIG.
23;
[0042] FIGS. 25(A), 25(B) and 25(C) are simplified cross-sectional
side views depicting a grinding process for providing a chamfer on
the MicroSDs according to the method of FIG. 3;
[0043] FIG. 26 is simplified top view showing process of marking
the MicroSD devices according to the method of FIG. 3;
[0044] FIG. 27 is simplified cross-sectional side view showing a
PCB panel including multi-stacked ICs according to an alternative
embodiment of the present invention;
[0045] FIG. 28(A), 28(B) and 28(C) are simplified perspective view
showing various memory devices produced using the production method
of the present invention;
[0046] FIGS. 29(A) and 29(B) are exploded perspective and assembled
perspective views showing a conventional method for producing
MicroSD devices; and
[0047] FIGS. 30(A) and 30(B) are exploded perspective and assembled
perspective views showing another conventional method for producing
MicroSD devices.
DETAILED DESCRIPTION OF THE DRAWINGS
[0048] The present invention relates to an improvement in
manufacturing methods for MicroSD (and "normal" SD) devices, and to
the improved MicroSD devices made by these methods. The following
description is presented to enable one of ordinary skill in the art
to make and use the invention as provided in the context of a
particular application and its requirements. As used herein, the
terms "upper", "upwards", "lower", and "downward" are intended to
provide relative positions for purposes of description, and are not
intended to designate an absolute frame of reference. Various
modifications to the preferred embodiment will be apparent to those
with skill in the art, and the general principles defined herein
may be applied to other embodiments. Therefore, the present
invention is not intended to be limited to the particular
embodiments shown and described, but is to be accorded the widest
scope consistent with the principles and novel features herein
disclosed.
[0049] FIGS. 1 and 2 are perspective and cross-sectional side views
showing a MicroSD device 100 according to a first embodiment of the
present invention. MicroSD device 100 generally includes a printed
circuit board assembly (PCBA) 110 and a plastic housing 150 that is
molded onto PCBA 110.
[0050] Referring to the upper portion of FIG. 1, PCBA 110 includes
a printed circuit board (PCB) substrate 111, and IC dies 130 and
135 and one or more passive components 142 that are mounted on PCB
substrate 111. PCB substrate 111 is a substantially flat substrate,
and has opposing sides that are referred to below as upper (first)
surface 112 and lower (second) surface 114. The four side edges of
substrate 111 are referenced as 111P-1 to 111P-4, and extend
between upper surface 112 and lower surface 114. Formed on upper
surface 112 are eight standardized (plug) metal contacts 120 that
are shaped and arranged in a pattern established by the MicroSD
specification. IC dies 130 and 135 and passive components 142 are
mounted on lower surface 114. PCB substrate 111 is formed in
accordance with known PCB manufacturing techniques such that metal
contacts 120, IC dies 130 and 135, and passive components 142 are
electrically interconnected by a predefined network including
conductive traces 131 and 136 and other conducting structures that
are sandwiched between multiple layers of an insulating material
(e.g., FR4 or BT) and adhesive.
[0051] According to an aspect of the invention, passive components
are mounted onto lower surface 114 using one or more standard
surface mount technology (SMT) techniques, and one or more
integrated circuit (IC) die (e.g., control IC die 130 and flash
memory die 135) are mounted using chip-on-board (COB) techniques.
As indicated in FIG. 2, during the SMT process, the passive
components, such as capacitor 142, are mounted onto contact pads
(described below) disposed on lower surface 114, and are then
secured to the contact pads using known solder reflow techniques.
To facilitate the SMT process, each of the passive components is
packaged in any of the multiple known (preferably lead-free) SMT
packages (e.g., ball grid array (BGA) or thin small outline package
(TSOP)). In contrast, IC dies 130 and 135 are unpackaged,
semiconductor "chips" that are mounted onto surface 114 and
electrically connected to corresponding contact pads using known
COB techniques. For example, as indicated in FIG. 2, control IC die
130 is electrically connected to PCB substrate 111 by way of wire
bonds 160-1 that are formed using known techniques. Similarly,
flash memory IC die 135 is electrically connected to PCB substrate
111 by way of wire bonds 160-2. Passive components 142, IC dies 130
and 135 and metal contacts 120 are operably interconnected by way
of metal traces 131 and 136 that are formed on and in PCB substrate
111 using known techniques, a few of which being depicted in FIG. 1
in a simplified manner by short dashed lines.
[0052] Housing 150 comprises molded plastic arranged such that
substantially all of the plastic used to form housing 150 is
located level with or below (i.e., on one side of) lower surface
114 of PCB substrate 111. Housing 150 includes a peripheral surface
extending perpendicular to PCB substrate 111, and a lower surface
152 that extends parallel to PCB substrate 111 and coplanar with a
side edge of PCB substrate 111. For discussion purposes, the
portion of the peripheral surface disposed at the front end of
MicroSD device 100 is referred to as front wall section 151P-1, the
portion of peripheral surface located at the rear end of device 100
is rear wall section 151P-3, and the opposing side portions of the
peripheral surface are side wall sections 151P-2 and 151P-4. As
shown is FIG. 2, housing 150 includes a chamfer section 154
extending upward from front wall section 151-1, and a raised,
step-like "finger-nail catch" structure 156 extending downward from
lower surface 152 adjacent to rear wall section 151P-3. These
features are provided to facilitate reliable insertion and removal
of MicroSD device 100 from a host system (e.g., a multi-media
mobile phone).
[0053] According to another aspect of the invention, MicroSD device
100 is subjected to a singulation (i.e., cutting and/or grinding)
process performed such that peripheral edges of both PCB substrate
111 and molded housing 150 have the same height, width and length
dimensions as those set forth by MicroSD memory card
specifications. That is, adjacent to metal contacts 120, both PCB
substrate 111 and molded housing 150 have a width W of 11 mm, which
is measured between peripheral side edges 111P-2 and 111P-4, and
between side walls 151P-2 and 151P-4. That is, peripheral side edge
111P-2 is substantially coplanar with side wall 151P-2, and side
edge 111P-4 is substantially coplanar with side wall 151P-4.
Similarly, as set forth below, at the completion of the singulation
process both PCB substrate 111 and molded housing 150 have a length
L of 15 mm, which is measured between peripheral front/rear edges
111P-1 and 111P-3, and between end walls 151P-1 and 151P-4. Note
that, as indicated in FIG. 2, due to the chamfering process
(described below), the final length of substrate 111 may be
slightly shorter than the predefined specified MicroSD length.
Finally, the combined thickness T of PCB substrate 111 and molded
housing 150 adjacent contacts 120 is 0.7 mm, per MicroSD
specifications. By producing MicroSD device 100 in this manner, the
surface area of PCB substrate 111 is significantly increased over
conventional methods, where the PCB must be narrower than the
memory card specification in order to fit inside a pre-molded
housing. MicroSD device 100 thus facilitates increased card
capacity and functionality due to the increased area of PCB
substrate 111 for mounting integrated circuits and other
components. In addition, molded housing (casing) 150 provides a
physically rigid memory card structure by filling gaps and spaces
that are otherwise not filled when separate covers are used. In
addition, molded housing 150 enables the use of a wide range of
memory devices (ICs) by allowing the molded material formed over
memory device 135 to be made extremely thin, or omitted
entirely.
[0054] FIG. 3 is a flow diagram showing a method for producing
MicroSD device 100 according to another embodiment of the present
invention. Summarizing the novel method, a PCB panel is generated
using known techniques (block 210), passive components are
produced/procured (block 212), and integrated circuit (IC) wafers
are fabricated or procured block 214). The passive components are
mounted on the PCB panel using SMT techniques (block 220), and the
IC dies are subject to a grind-back process (block 242) and dicing
process (block 244) before being die bonded (block 246) and wire
bonded (block 248) onto the PCB panel using known COB techniques.
Molten plastic is then used to form a molded thermal plastic layer
over the passive components and the IC dies (block 250). Then PCB
panel is then singulated (cut) in to separate MicroSD devices
(block 260), and the individual MicroSD devices are subjected to a
chamfer process (block 265). The MicroSD devices are then marked
(block 270), and then the MicroSD devices are tested, packed and
shipped (block 280) according to customary practices. This method
provides several advantages over conventional manufacturing methods
that utilize SMT techniques only. First, by utilizing COB
techniques to mount the MicroSD controller and flash memory, the
large amount of space typically taken up by these devices is
dramatically reduced, thereby facilitating significant
miniaturization of the resulting MicroSD device footprint. Second,
by implementing the wafer grinding methods described below, the die
height is greatly reduced, thereby facilitating a stacked memory
arrangement that a significant memory capacity increase over
packaged flash memory arrangements. The molded housing also
provides greater moisture and water resistance and higher impact
force resistance than that achieved using conventional
manufacturing methods. In comparison to the standard MicroSD memory
card manufacturing that used SMT process, it is cheaper to use the
combined COB and SMT (plus molding) processes described herein
because, in the SMT-only manufacturing process, the bill of
materials such as Flash memory and the controller chip are also
manufactured by COB process, so all the COB costs are already
factored into the packaged memory chip and controller chip.
Therefore, the combined COB and SMT method according to the present
invention provides a less expensive and higher quality (i.e., more
reliable) memory product with a smaller size than that possible
using conventional SMT-only manufacturing methods.
[0055] The flow diagram of FIG. 3 will now be described in
additional detail below with reference to FIGS. 4(A) to 20.
[0056] Referring to the upper portion of FIG. 3, the manufacturing
method begins with filling a bill of materials including
producing/procuring PCB panels (block 210), producing/procuring
passive (discrete) components (block 212) such as resistors,
capacitors, diodes, and oscillators that are packaged for SMT
processing, and producing/procuring a supply of IC wafers (or
individual IC dies, block 214).
[0057] FIGS. 4(A) and 4(B) are simplified top and bottom views,
respectively, showing a PCB panel 300(t0) provided in block 210 of
FIG. 3 according to a specific embodiment of the present invention.
The suffix "tx" is utilized herein to designated the state of the
PCB panel during the manufacturing process, with "t0" designating
an initial state. Sequentially higher numbered prefixes (e.g.,
"t1", "t2" and "t3") indicate that PCB panel 300 has undergone
additional sequential production processes.
[0058] As indicated in FIG. 4(A) and 4(B), PCB panel 300(t0)
includes a five-by-three matrix of PCB regions 311 that are
surrounded by opposing end border structures 310 and side border
structures 312, which are integrally connected to form a square or
rectangular frame of blank material around PCB regions 311. Each
PCB region 311 (which is indicated by dashed lines for convenience
and corresponds to substrate 111; see FIG. 1) has the features
described above with reference to FIGS. 1 and 2, and the additional
features described below. FIG. 4(A) shows lower surface 114 of each
PCB region 311, and FIG. 4(B) shows upper surface 112 of each PCB
region 311, which includes standard metal contacts 120. Note that
lower surface 114 of each PCB region 311 (e.g., PCB region 311-11)
includes multiple contact pads 119 arranged in predetermined
patterns for facilitating SMT and COB processes, as described
below. Referring to FIG. 4(A), each PCB region 311 in each row is
connected to either an end border structure 310, a side region 312
or to an adjacent PCB region 311 by way of an intervening portion
315 of panel 300. For example, referring to the upper row of PCBs
in FIG. 4(A), PCB region 311-11 is connected to the left end region
310, the upper side region 312, and by intervening portion 315-11
to PCB region 311-12.
[0059] As indicated in FIG. 4(B), in accordance with an aspect of
the present invention, optional designated cut lines 317 and 318
are scored or otherwise partially cut into one of side border
structure 312 and/or central region of PCB panel 300 that are
aligned with the front and rear edges of PCB regions 311 aligned in
each row and column, respectively. In an alternative embodiment,
cut lines 317 and 318 may be omitted, or comprise surface markings
that do not weaken the panel material.
[0060] In accordance with yet another aspect of the present
invention, border structures 310 and 312 are provided with
positioning holes 319 to facilitate alignment between PCB panel 300
and the plastic molding die during molded housing formation, as
described below.
[0061] FIG. 5 is a perspective view depicting a PCB region 311-11
of panel 300(t0) during a SMT process that is used to mount passive
components on PCB region 311-11 according to block 220 of FIG. 3.
Note that PCB region 311-11 (which corresponds to PCB substrate 111
of FIG. 1) is shown separate from panel 300(t0) for illustrative
purposes, and is actually integrally formed with the remainder of
panel 300(t0) during the process steps described below preceding
singulation. During the first stage of the SMT process, lead-free
solder paste (not shown) is printed on contact pads 119-1, 119-2
and 119-3, which in the present example corresponds to SMT
components 142, 144 and 146, using custom made stencil that is
tailored to the design and layout of PCB region 311-11. After
dispensing the solder paste, the panel is conveyed to a
conventional pick-and-place machine that mounts SMT components 142,
144 and 146 onto contact pads 119-1, 119-2 and 119-3, respectively,
according to known techniques. Upon completion of the
pick-and-place component mounting process, PCB panel 300(t0) is
then passed through an IR-reflow oven set at the correct
temperature profile. The solder of each pad on the PC board is
fully melted during the peak temperature zone of the oven, and this
melted solder connects all pins of the passive components to the
finger pads of the PC board. FIG. 6 shows the resulting
sub-assembled PCB panel 300(t1), in which each PCB region 311
(e.g., PCB region 311-11) includes passive components 142, 144 and
146 mounted thereon by the completed SMT process.
[0062] FIG. 7 is a simplified perspective view showing a
semiconductor wafer 400(t0) procured or fabricated according to
block 214 of FIG. 3. Wafer 400(t0) includes multiple ICs 430 that
are formed in accordance with known photolithographic fabrication
(e.g., CMOS) techniques on a semiconductor base 401. The corner
partial dies 402 are inked out during die probe wafer testing, as
are complete dies that fail electrical function or DC/AC parametric
tests. In the example described below, wafer 400(t1) includes ICs
430 that comprise MicroSD controller circuits. In a related
procedure, a wafer (not shown) similar to wafer 400(t1) is
produced/procured that includes flash memory circuits, and in an
alterative embodiment, ICs 430 may include both MicroSD controller
circuits and flash memory circuits. In each instance, these wafers
are processed as described herein with reference to FIGS. 8(A),
8(B) and 8(C).
[0063] As indicated in FIGS. 8(A) and 8(B), during a wafer back
grind process according to block 242 of FIG. 3, base 401 is
subjected to a grinding process in order to reduce the overall
initial thickness TW1 of each IC 430. Wafer 400(t1) is first mount
face down on sticky tape (i.e., such that base layer 401(t0) faces
away from the tape), which is pre-taped on a metal or plastic ring
frame (not shown). The ring-frame/wafer assembly is then loaded
onto a vacuum chuck (not shown) having a very level, flat surface,
and has diameter larger than that of wafer 400(t0). The base layer
is then subjected to grinding until, as indicated in FIG. 8(B),
wafer 400(t1) has a pre-programmed thickness TW2 that is less than
initial thickness TW1 (shown in FIG. 8(A)). The wafer is cleaned
using de-ionized (DI) water during the process, and wafer 400(t1)
is subjected to a flush clean with more DI water at the end of
mechanical grinding process, followed by spinning at high speed to
air dry wafer 400(t1).
[0064] Next, as shown in FIG. 8(C), the wafer is diced (cut apart)
along predefined border structures separating ICs 420 in order to
produce IC dies 130 according to block 244 of FIG. 3. After the
back grind process has completed, the sticky tape at the front side
of wafer 400(t1) is removed, and wafer 400(t1) is mounted onto
another ring frame having sticky tape provided thereon, this time
with the backside of the newly grinded wafer contacting the tape.
The ring framed wafers are then loaded into a die saw machine. The
die saw machine is pre-programmed with the correct die size
information, X-axis and Y-axis scribe lanes, width, wafer thickness
and intended over cut depth. A proper saw blade width is then
selected based on the widths of the XY scribe lanes. The cutting
process begins dicing the first lane of the X-axis of the wafer.
De-ionized wafer is flushing at the proper angle and pressure
around the blade and wafer contact point to wash and sweep away the
silicon saw dust while the saw is spinning and moving along the
scribe lane. The sawing process will index to the second lane
according to the die size and scribe width distance. After all the
X-axis lanes have been completed sawing, the wafer chuck with
rotate 90 degree to align the Y-axis scribe lanes to be cut. The
cutting motion repeated until all the scribe lanes on the Y-axis
have been completed.
[0065] FIG. 9 is a perspective view depicting a die bonding process
utilized to mount the controller IC dies 130 of FIG. 8(C) and flash
memory IC dies 135 on PCB region 311-11 of the PCB panel according
to block 246 of FIG. 3. The die bonding process is performed on PCB
panel 300(t1) (see FIG. 6), that is, after completion of the SMT
process. The die bonding process generally involves mounting
controller IC dies 130 into lower surface region 114A, which is
bordered by contact pads 119-5, and mounting flash IC dies 135 into
lower surface region 114B, which is disposed between rows of
contact pads 119-6. In one specific embodiment, an operator loads
IC dies 130 and 135 onto a die bonder machine according to known
techniques. The operator also loads multiple PCB panels 300(t1)
onto the magazine rack of the die bonder machine. The die bonder
machine picks the first PCB panel 300(t1) from the bottom stack of
the magazine and transports the selected PCB panel from the
conveyor track to the die bond (DB) epoxy dispensing target area.
The magazine lowers a notch automatically to get ready for the
machine to pick up the second piece (the new bottom piece) in the
next cycle of die bond operation. At the die bond epoxy dispensing
target area, the machine automatically dispenses DB epoxy, using
pre-programmed write pattern and speed with the correct nozzle
size, onto the target areas 114A and 114B of each of the PCB region
311 of PCB panel 300(t1). When all PCBs region 311 have completed
this epoxy dispensing process, the PCB panel is conveyed to a die
bond (DB) target area. Meanwhile, at the input stage, the magazine
is loading a second PCB panel to this vacant DB epoxy dispensing
target area. At the die bond target area, the pick up arm mechanism
and collet (suction head with rectangular ring at the perimeter so
that vacuum from the center can create a suction force) picks up an
IC die 130 and bonds it onto area 114A, where epoxy has already
dispensed for the bonding purpose, and this process is then
performed to place IC die 135 into region 114B. Once all the PCB
regions 311 on the PCB panel have completed die bonding process,
the PCB panel is then conveyed to a snap cure region, where the PCB
panel passes through a chamber having a heating element that
radiates heat having a temperature that is suitable to thermally
cure the epoxy. After curing, the PCB panel is conveyed into the
empty slot of the magazine waiting at the output rack of the die
bonding machine. The magazine moves up one slot after receiving a
new panel to get ready for accepting the next panel in the second
cycle of process. The die bonding machine will repeat these steps
until all of the PCB panels in the input magazine are processed.
This process step may repeat again for the same panel for stack die
products that may require to stacks more than one layer of memory
die. FIG. 10 is a top view showing PCB panel 300(t2) after the die
bonding process is completed and controller IC 130 and memory IC
135 are mounted onto each PCB (e.g., PCB region 311-11).
[0066] FIG. 11 is a perspective view depicting a wire bonding
process utilized to connect the IC dies 130 and 135 to
corresponding contact pads 119-5 and 119-6 of PCB region 311-11,
respectively, according to block 248 of FIG. 3. The wire bonding
process proceeds as follows. Once a full magazine of PCB panels
300(t2) (see FIG. 10) has completed the die bonding operation, an
operator transports the PCB panels 300(t2) to a nearby wire bonder
(WB) machine, and loads the PCB panels 300(t2) onto the magazine
input rack of the WB machine. The WB machine is pre-prepared with
the correct program to process this specific MicroSD device. The
coordinates of all the ICs' pads 119-5 and 119-6 and PCB gold
fingers were previously determined and programmed on the WB
machine. After the PCB panel with the attached dies 130 and 135 is
loaded at the WB bonding area, the operator commands the WB machine
to use optical vision to recognize the location of the first wire
bond pad 131 of the first controller die 130 of PCB region 311-11
on the panel. A corresponding wire 160-1 is then formed between
wire bond pad 131 and a corresponding contact pad 119-5 formed on
PCB region 311-11. Once the first pin is set correctly and the
first wire bond 160-1 is formed, the WB machine can carry out the
whole wire bonding process for the rest of controller die 130, and
then proceed to forming wire bonds 160-2 between corresponding wire
bond pads (not shown) on memory die 135 and contact pads 119-6 to
complete the wire bonding of memory die 135. Upon completing the
wiring bonding process for PCB region 311-11, the wire bonding
process is repeated for each PCB region 311 of the panel. For
multiple flash layer stack dies, the PCB panels may be returned to
the WB machine to repeat wire bonding process for the second stack.
FIG. 12 is a top view showing PCB panel 300(t3) after the wire
bonding process is completed.
[0067] FIG. 13 is a perspective top view showing a lower die 410 of
a simplified top and enlarged partial top views depicting a lower
(first) molding die including a shallow cavity 411 surrounded by a
peripheral surface 412 that is shaped to receive PCB panel 300(t3)
(see FIG. 12) in the manner described below. In addition, lower die
410 includes three raised alignment poles 419 that are positioned
to receive alignment holes 319 of PCB panel 300 (see FIG. 4(A)).
Alignment poles 419 have a height that is not greater than the
thickness of PCB panel 300.
[0068] FIG. 14 is a top view showing an upper molding die 420 that
is used in conjunction with lower molding die 410 (FIG. 13). Upper
molding die 420 includes a central depending region 421 surrounded
by a peripheral raised surface 422 that are mounted over and
pressed against cavity 411 and peripheral surface 412 of lower
molding die 410 during the molding process. Region 421 of upper
molding die 420 defines a molding chamber region into which molten
plastic is injected to form a molded layer over the surface of an
inserted PCB panel. Recessed regions 426 are provided upper molding
die 420 that facilitate the formation of finger-nail catches 156
(see FIG. 1). Note that a run gate (channel) 429 is provided for
each row of PCB regions that facilitates the injection of molten
plastic into the region 421.
[0069] FIG. 15 is a top plan view depicting mounting PCB panel
300(t3) into lower molding die 410. Each alignment pole 419 is
received inside a corresponding alignment hole 319 of panel
300(t3), as shown in the top left corner of FIG. 15.
[0070] FIGS. 16(A), 16(B) and 16(C) are simplified cross-sectional
side views depicting a molding process using molding dies 410 and
420. As indicated in FIG. 16(A) and 16(B), after panel 300(t3) is
loaded into lower molding die 410, upper molding die 420 is
positioned over and lowered onto lower molding die 410 until
peripheral raised surface 422 presses against corresponding
peripheral end/side portions 310/312 of PCB panel 300(t3)
surrounding PCB regions 311, thereby forming a substantially
enclosed chamber 425 over all fifteen PCB regions 311, as indicated
in FIG. 16(B). Referring again to FIG. 16(B), in accordance with
another aspect of the invention, a single run gate (channel) set
429 is provided for each row of PCB regions 311 that facilitates
the injection of molten plastic into chamber 425, as indicated in
FIG. 16(C), whereby single-piece molded layer 450 is formed on a
central portion of lower surface 114 over all fifteen PCB regions
311. From this point forward, the PCB panel is referred to as
300(t4).
[0071] FIG. 16(C) depicts the molding process. Transfer molding is
prefer here due to the high accuracy of transfer molding tooling
and low cycle time. The molding material in the form of pellet is
preheated and loaded into a pot or chamber (not shown). A plunger
(not shown) is then used to force the material from the pot through
channel sets 429 (also known as a spruce and runner system) into
the mold cavity 425, causing the molten (e.g., plastic) material to
form molded layer 450 that encapsulates all the IC chips and
components, and to cover all the exposed areas of lower surface
114. Note that, because PCB 300(t4) is pressed against lower mold
420 by peripheral raised surface 422, no molding material is able
to form on upper surface 112. The mold remains closed as the
material is inserted and filled up all vacant areas of the mold
die. During the process, the walls of upper die 420 are heated to a
temperature above the melting point of the mold material, which
facilitates a faster flow of material. The mold assembly remains
closed until a curing reaction within the molding material is
complete. A cooling down cycle follows the injection process, and
the molding materials start to solidify and harden. Ejector pins
push PCB panel 300(t4) (shown in FIG. 16(C) and 17) from the mold
machine once the molding material has hardened sufficiently.
[0072] FIG. 17 is a perspective bottom view showing PCB panel
300(t4) after the plastic molding process of FIGS. 16(A) to 16(C)
is completed. Panel 300(t4) includes molded layer 450 formed on
lower surface 114 that covers all fifteen PCB regions 311 (which
are generally indicated by dashed lines). Molded layer 450 has a
substantially flat upper surface 458, and fifteen raised, step-like
"finger-nail catch" structures 156 disposed over PCB regions
311.
[0073] Referring again to block 260 of FIG. 3, a subsequent
processing step involves singulating (separating) the over-molded
PCB panel to form individual MicroSD devices by cutting said PCB
panel and said molded layer using one of a laser cut, a water jet
cut or a saw/mechanical grind process, thereby separating said PCB
panel into a plurality of individual MicroSD devices. Each of these
singulation methods is described below with reference to FIGS.
18-23. Those skilled in the art will recognize that other
singulation methods may also be utilized without departing from the
spirit and scope of the present invention.
[0074] FIG. 18 is a simplified top plan view depicting a direct
singulation process in which MicroSD device 100-11 is removed from
PCB panel 300(t4) is one cutting pass using a cutting tool 500.
That is, cutting tool 500 generates a beam or jet 505 that is
directed along a peripheral edge of region 311-11 that passes
through both PCB panel 300(t4) and the molding layer (which is
disposed below panel 450 in FIG. 18), thereby separating PCB
substrate 111-11 and a corresponding molded housing (not shown, but
located on the opposite side of substrate 111-11) from region
311-11 (whereby region 311-11 becomes an open hole). In alternative
embodiments described in additional detail below, cutting tool 500
is implemented using a laser cutting tool and a water jet cutting
tool, whereby MicroSD device 100-11 is detached and can be removed.
After the fifteen MicroSD devices are removed, the remaining
skeleton portion of PCB panel 300(t4) is recycled.
[0075] FIG. 19 is a simplified side view depicting PCB panel
300(t4) during singulation into individual MicroSD devices using a
full laser cutting system 500A according to a specific embodiment
of the present invention. A laser beam 505A, generated, for
example, by a laser diode (not shown) disposed inside laser cutter
500A, is directed onto upper surface 112 along the peripheral
outline of each MicroSD device. Laser beam 505A passes entirely
through both PCB panel 300(t4) and molded layer 450, whereby each
microSD device (e.g., device 100-11) becomes detached from PCB
panel 300(t4) by way of a continuous channel 510-11, and is
separated as shown in FIG. 18. Note that each microSD device (e.g.,
device 100-11) includes both a PCB substrate (e.g., substrate
111-11) and a molded housing (e.g., housing 150-11) that are
disposed in the targeted region (e.g., region 311-11). Laser
cutters 500A provide excellent cutting quality with cutting angle
capability of less than 1 degree. Automatic cutting position
alignment is achieved using a conventional vision system and
associated control circuit (not shown). Once the starting position
and the outline shape and dimensions are set, the laser system will
cut out each micro-SD according to the pre-feed in dimensions
specification. Laser cutting system 500A can optimize the
utilization of substrates of a panel by minimizing the wasted space
between adjacent devices. A suitable laser cutting system 500A is
produced by BE Semiconductor Industries N.V. (the Netherlands)
under the model name Fico Bright Line.
[0076] FIG. 20 is a simplified side view depicting PCB panel
300(t4) during singulation into individual MicroSD devices using an
abrasive water jet (AWJ) cutting system 500B according to another
specific embodiment of the present invention. A head 501 includes
separate channels for feeding water 502 and abrasive powder 503
into a mixing chamber 504 at a predetermined pressure that forces
the mixture from head 501 in the form of a jet 505B. Similar to
laser beam 505A, jet 505B is directed onto upper surface 112 along
the peripheral outline of each MicroSD device, and has sufficient
force to pass entirely through both PCB panel 300(t4) and molded
layer 450, whereby each microSD device (e.g., device 100-11)
becomes detached from PCB panel 300(t4) by way of a continuous
channel 520-11, and is separated as shown in FIG. 18. The
abrasive/water mixture is then collected and recycled. A suitable
AWJ cutting system 500B is produced by TOPS Co. Ltd. (Korea) under
the model no/name SJA-0505.
[0077] FIGS. 21 to 24 depict yet another singulation process
according to block 260 of FIG. 3 that is used to separate PCB panel
300(t4) into individual MicroSD devices. Referring to FIG. 21, PCB
panel 300(t4) is loaded into a saw machine (not shown) that is
pre-programmed with a singulation routine that includes
predetermined cut locations defined by designated cut lines 317. A
saw blade 530 is aligned to the first cut line (e.g., end cut line
317-1) as a starting point by the operator. The coordinates of the
first position are stored in the memory of the saw machine. The saw
machine then automatically proceeds to cut up (singulate) panel
300(t4), for example, successively along cut lines 317, first in
one direction (e.g., along vertical cut lines 317 in FIG. 21), and
then in the orthogonal direction (e.g., along horizontal cut lines
317 in FIG. 21). FIG. 22 is a top view showing blocks 600 cut from
panel 300(t4) using the sawing process of FIG. 21, each block 600
including an individual MicroSD device (as indicated by the dashed
outline). As indicated in FIG. 23, a mechanical grinder 540 (shown
in simplified form) is then utilized to remove excess PCB and
molded plastic material disposed along the peripheral edge of each
block 600, e.g., by passing grinder 540 along peripheral edges
111P-1 to 111P-4 as indicated. In one embodiment, a dimensionally
accurate MicroSD device (not shown) is used as a reference to guide
the grinding process for each block 600. FIG. 24 is simplified top
view depicting the individual MicroSD devices 100 after completion
of the grinding process of FIG. 23.
[0078] FIGS. 25(A) to 25(C) are simplified side views showing a
chamfer process according to block 265 of FIG. 3, which is
performed as a final processing step to individual MicroSD devices
101A that have been singulated from their PCB panel according to
any of the above-mentioned singulation processes. FIG. 25(A) shows
a device 101A positioned over a fixture 560 having a lower wall 561
and a front wall 562 that define a front corner opening 563. As
indicated in FIG. 25(B), when device 100A is mounted onto fixture
560, a front corner portion P of device 100A extends through
opening 563. A grinding wheel or belt 570 is then used to remove
the front corner portion, thereby forming the desired chamfer
surface 154 on MicroSD device 100, which is shown in FIG.
25(C).
[0079] FIG. 26 is a perspective bottom view showing a MicroSD
device 100 after singulation and chamfering, and further showing a
marking process in accordance with block 270 of the method of FIG.
3. The singulated and completed MicroSD devices 100 undergo a
marking process in which a designated company's name/logo, speed
value, density value, or other related information are printed on
surface 152 of housing 150. After marking, MicroSD devices 100 are
placed in the baking oven to cure the permanent ink.
[0080] Referring to block 280 located at the bottom of FIG. 3, a
final procedure in the manufacturing method of the present
invention involves testing, packing and shipping the individual
MicroSD devices. The marked MicroSD devices 100 shown in FIG. 26
are then subjected to visual inspection and electrical tests
consistent with well established techniques. Visually or/and
electrically test rejects are removed from the good population as
defective rejects. The good memory cards are then packed into
custom made boxes which are specified by customers. The final
packed products will ship out to customers following correct
procedures with necessary documents.
[0081] FIG. 27 is a simplified side view showing a PCB substrate
300B including multiple MicroSD devices 100B according to an
alternative embodiment of the present invention. As suggested in
the above example, in addition to reducing overall manufacturing
costs by utilizing unpackaged controller and flash memory dies
(i.e., by eliminating the packaging costs associated with SMT-ready
controller and flash memory devices), the present invention
provides a further benefit of facilitating greatly expanded memory
capacity without increasing the overall size of each MicroSD device
100B, e.g., by facilitating a stacked-memory MicroSD device in
which a first flash memory chip 135B-1 is mounted on the PCB and
connected by first wire bonds, and a second flash memory chip
135B-2 is mounted on the first memory chip and connected by a
second set of wire bonds to the PCB. Because the IC die height
(thickness) D is much smaller than the thickness of packaged flash
memory devices, and because thickness T of each MicroSD device 100B
is set by predetermined standards, the present invention
facilitates such a stacked memory arrangement that greatly
increases memory capacity without increasing the footprint of
MicroSD device 100B.
[0082] Although the present invention has been described with
respect to certain specific embodiments, it will be clear to those
skilled in the art that the inventive features of the present
invention are applicable to other embodiments as well, all of which
are intended to fall within the scope of the present invention. For
example, FIGS. 28(A) to 28(C) show Secure Digital devices 100C,
100D and 100E, which represent alternative memory card devices that
may be produced in accordance with the methods of the present
invention, each card having associated PCB substrates and
associated molded housings that define height, width and length
measurements established by SD specifications.
* * * * *